Always defer *sql.Rows.Close and consult with Err (#844)

* Always defer *sql.Rows.Close and consult with Err

database/sql.Rows.Next() makes sure to call Close only after exhausting
result rows which would NOT happen when returning early from a bad Scan.
Close being idempotent makes it a great candidate to get always deferred
regardless of what happens later on the result set.

This change also makes sure call Err() after exhausting Next() and
propagate non-nil results from it as the documentation advises.

Closes #764

Signed-off-by: Kiril Vladimiroff <kiril@vladimiroff.org>

* Override named result parameters in last returns

Signed-off-by: Kiril Vladimiroff <kiril@vladimiroff.org>

* Do the same over new changes that got merged

Signed-off-by: Kiril Vladimiroff <kiril@vladimiroff.org>

Co-authored-by: Neil Alexander <neilalexander@users.noreply.github.com>

9 files changed, 50 insertions, 24 deletions

diff --git a/roomserver/storage/postgres/event_json_table.go b/roomserver/storage/postgres/event_json_table.go
index 415fb84e..0b7ef6aa 100644
--- a/roomserver/storage/postgres/event_json_table.go
+++ b/roomserver/storage/postgres/event_json_table.go
@@ -102,5 +102,5 @@ func (s *eventJSONStatements) bulkSelectEventJSON(
 		}
 		result.EventNID = types.EventNID(eventNID)
 	}
-	return results[:i], nil
+	return results[:i], rows.Err()
 }
diff --git a/roomserver/storage/postgres/event_state_keys_table.go b/roomserver/storage/postgres/event_state_keys_table.go
index c3aaa498..cbc29a69 100644
--- a/roomserver/storage/postgres/event_state_keys_table.go
+++ b/roomserver/storage/postgres/event_state_keys_table.go
@@ -125,7 +125,7 @@ func (s *eventStateKeyStatements) bulkSelectEventStateKeyNID(
 		}
 		result[stateKey] = types.EventStateKeyNID(stateKeyNID)
 	}
-	return result, nil
+	return result, rows.Err()
 }
 
 func (s *eventStateKeyStatements) bulkSelectEventStateKey(
@@ -150,5 +150,5 @@ func (s *eventStateKeyStatements) bulkSelectEventStateKey(
 		}
 		result[types.EventStateKeyNID(stateKeyNID)] = stateKey
 	}
-	return result, nil
+	return result, rows.Err()
 }
diff --git a/roomserver/storage/postgres/event_types_table.go b/roomserver/storage/postgres/event_types_table.go
index 1ec2e7cd..faa88754 100644
--- a/roomserver/storage/postgres/event_types_table.go
+++ b/roomserver/storage/postgres/event_types_table.go
@@ -143,5 +143,5 @@ func (s *eventTypeStatements) bulkSelectEventTypeNID(
 		}
 		result[eventType] = types.EventTypeNID(eventTypeNID)
 	}
-	return result, nil
+	return result, rows.Err()
 }
diff --git a/roomserver/storage/postgres/events_table.go b/roomserver/storage/postgres/events_table.go
index 1e8a5665..d9b269bc 100644
--- a/roomserver/storage/postgres/events_table.go
+++ b/roomserver/storage/postgres/events_table.go
@@ -209,6 +209,9 @@ func (s *eventStatements) bulkSelectStateEventByID(
 			return nil, err
 		}
 	}
+	if err = rows.Err(); err != nil {
+		return nil, err
+	}
 	if i != len(eventIDs) {
 		// If there are fewer rows returned than IDs then we were asked to lookup event IDs we don't have.
 		// We don't know which ones were missing because we don't return the string IDs in the query.
@@ -219,7 +222,7 @@ func (s *eventStatements) bulkSelectStateEventByID(
 			fmt.Sprintf("storage: state event IDs missing from the database (%d != %d)", i, len(eventIDs)),
 		)
 	}
-	return results, err
+	return results, nil
 }
 
 // bulkSelectStateAtEventByID lookups the state at a list of events by event ID.
@@ -251,12 +254,15 @@ func (s *eventStatements) bulkSelectStateAtEventByID(
 			)
 		}
 	}
+	if err = rows.Err(); err != nil {
+		return nil, err
+	}
 	if i != len(eventIDs) {
 		return nil, types.MissingEventError(
 			fmt.Sprintf("storage: event IDs missing from the database (%d != %d)", i, len(eventIDs)),
 		)
 	}
-	return results, err
+	return results, nil
 }
 
 func (s *eventStatements) updateEventState(
@@ -321,6 +327,9 @@ func (s *eventStatements) bulkSelectStateAtEventAndReference(
 		result.EventID = eventID
 		result.EventSHA256 = eventSHA256
 	}
+	if err = rows.Err(); err != nil {
+		return nil, err
+	}
 	if i != len(eventNIDs) {
 		return nil, fmt.Errorf("storage: event NIDs missing from the database (%d != %d)", i, len(eventNIDs))
 	}
@@ -343,6 +352,9 @@ func (s *eventStatements) bulkSelectEventReference(
 			return nil, err
 		}
 	}
+	if err = rows.Err(); err != nil {
+		return nil, err
+	}
 	if i != len(eventNIDs) {
 		return nil, fmt.Errorf("storage: event NIDs missing from the database (%d != %d)", i, len(eventNIDs))
 	}
@@ -366,6 +378,9 @@ func (s *eventStatements) bulkSelectEventID(ctx context.Context, eventNIDs []typ
 		}
 		results[types.EventNID(eventNID)] = eventID
 	}
+	if err = rows.Err(); err != nil {
+		return nil, err
+	}
 	if i != len(eventNIDs) {
 		return nil, fmt.Errorf("storage: event NIDs missing from the database (%d != %d)", i, len(eventNIDs))
 	}
@@ -389,7 +404,7 @@ func (s *eventStatements) bulkSelectEventNID(ctx context.Context, eventIDs []str
 		}
 		results[eventID] = types.EventNID(eventNID)
 	}
-	return results, nil
+	return results, rows.Err()
 }
 
 func (s *eventStatements) selectMaxEventDepth(ctx context.Context, eventNIDs []types.EventNID) (int64, error) {
diff --git a/roomserver/storage/postgres/invite_table.go b/roomserver/storage/postgres/invite_table.go
index 43cd5ba0..603fed31 100644
--- a/roomserver/storage/postgres/invite_table.go
+++ b/roomserver/storage/postgres/invite_table.go
@@ -114,21 +114,23 @@ func (s *inviteStatements) insertInviteEvent(
 func (s *inviteStatements) updateInviteRetired(
 	ctx context.Context,
 	txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
-) (eventIDs []string, err error) {
+) ([]string, error) {
 	stmt := common.TxStmt(txn, s.updateInviteRetiredStmt)
 	rows, err := stmt.QueryContext(ctx, roomNID, targetUserNID)
 	if err != nil {
 		return nil, err
 	}
-	defer (func() { err = rows.Close() })()
+	defer rows.Close() // nolint: errcheck
+
+	var eventIDs []string
 	for rows.Next() {
 		var inviteEventID string
-		if err := rows.Scan(&inviteEventID); err != nil {
+		if err = rows.Scan(&inviteEventID); err != nil {
 			return nil, err
 		}
 		eventIDs = append(eventIDs, inviteEventID)
 	}
-	return
+	return eventIDs, rows.Err()
 }
 
 // selectInviteActiveForUserInRoom returns a list of sender state key NIDs
@@ -151,5 +153,5 @@ func (s *inviteStatements) selectInviteActiveForUserInRoom(
 		}
 		result = append(result, types.EventStateKeyNID(senderUserNID))
 	}
-	return result, nil
+	return result, rows.Err()
 }
diff --git a/roomserver/storage/postgres/membership_table.go b/roomserver/storage/postgres/membership_table.go
index 9f41fd67..70032fd1 100644
--- a/roomserver/storage/postgres/membership_table.go
+++ b/roomserver/storage/postgres/membership_table.go
@@ -151,6 +151,7 @@ func (s *membershipStatements) selectMembershipsFromRoom(
 	if err != nil {
 		return
 	}
+	defer rows.Close() // nolint: errcheck
 
 	for rows.Next() {
 		var eNID types.EventNID
@@ -159,8 +160,9 @@ func (s *membershipStatements) selectMembershipsFromRoom(
 		}
 		eventNIDs = append(eventNIDs, eNID)
 	}
-	return
+	return eventNIDs, rows.Err()
 }
+
 func (s *membershipStatements) selectMembershipsFromRoomAndMembership(
 	ctx context.Context,
 	roomNID types.RoomNID, membership membershipState,
@@ -170,6 +172,7 @@ func (s *membershipStatements) selectMembershipsFromRoomAndMembership(
 	if err != nil {
 		return
 	}
+	defer rows.Close() // nolint: errcheck
 
 	for rows.Next() {
 		var eNID types.EventNID
@@ -178,7 +181,7 @@ func (s *membershipStatements) selectMembershipsFromRoomAndMembership(
 		}
 		eventNIDs = append(eventNIDs, eNID)
 	}
-	return
+	return eventNIDs, rows.Err()
 }
 
 func (s *membershipStatements) updateMembership(
diff --git a/roomserver/storage/postgres/room_aliases_table.go b/roomserver/storage/postgres/room_aliases_table.go
index ad1b560c..6de898c4 100644
--- a/roomserver/storage/postgres/room_aliases_table.go
+++ b/roomserver/storage/postgres/room_aliases_table.go
@@ -90,23 +90,23 @@ func (s *roomAliasesStatements) selectRoomIDFromAlias(
 
 func (s *roomAliasesStatements) selectAliasesFromRoomID(
 	ctx context.Context, roomID string,
-) (aliases []string, err error) {
-	aliases = []string{}
+) ([]string, error) {
 	rows, err := s.selectAliasesFromRoomIDStmt.QueryContext(ctx, roomID)
 	if err != nil {
-		return
+		return nil, err
 	}
+	defer rows.Close() // nolint: errcheck
 
+	var aliases []string
 	for rows.Next() {
 		var alias string
 		if err = rows.Scan(&alias); err != nil {
-			return
+			return nil, err
 		}
 
 		aliases = append(aliases, alias)
 	}
-
-	return
+	return aliases, rows.Err()
 }
 
 func (s *roomAliasesStatements) selectCreatorIDFromAlias(
diff --git a/roomserver/storage/postgres/state_block_table.go b/roomserver/storage/postgres/state_block_table.go
index 15e69cc9..e6f4f7fe 100644
--- a/roomserver/storage/postgres/state_block_table.go
+++ b/roomserver/storage/postgres/state_block_table.go
@@ -152,7 +152,7 @@ func (s *stateBlockStatements) bulkSelectStateBlockEntries(
 			eventNID         int64
 			entry            types.StateEntry
 		)
-		if err := rows.Scan(
+		if err = rows.Scan(
 			&stateBlockNID, &eventTypeNID, &eventStateKeyNID, &eventNID,
 		); err != nil {
 			return nil, err
@@ -169,10 +169,13 @@ func (s *stateBlockStatements) bulkSelectStateBlockEntries(
 		}
 		current.StateEntries = append(current.StateEntries, entry)
 	}
+	if err = rows.Err(); err != nil {
+		return nil, err
+	}
 	if i != len(stateBlockNIDs) {
 		return nil, fmt.Errorf("storage: state data NIDs missing from the database (%d != %d)", i, len(stateBlockNIDs))
 	}
-	return results, nil
+	return results, err
 }
 
 func (s *stateBlockStatements) bulkSelectFilteredStateBlockEntries(
@@ -237,7 +240,7 @@ func (s *stateBlockStatements) bulkSelectFilteredStateBlockEntries(
 	if current.StateEntries != nil {
 		results = append(results, current)
 	}
-	return results, nil
+	return results, rows.Err()
 }
 
 func stateBlockNIDsAsArray(stateBlockNIDs []types.StateBlockNID) pq.Int64Array {
diff --git a/roomserver/storage/postgres/state_snapshot_table.go b/roomserver/storage/postgres/state_snapshot_table.go
index 76f1d2b6..a1f26e22 100644
--- a/roomserver/storage/postgres/state_snapshot_table.go
+++ b/roomserver/storage/postgres/state_snapshot_table.go
@@ -104,7 +104,7 @@ func (s *stateSnapshotStatements) bulkSelectStateBlockNIDs(
 	for ; rows.Next(); i++ {
 		result := &results[i]
 		var stateBlockNIDs pq.Int64Array
-		if err := rows.Scan(&result.StateSnapshotNID, &stateBlockNIDs); err != nil {
+		if err = rows.Scan(&result.StateSnapshotNID, &stateBlockNIDs); err != nil {
 			return nil, err
 		}
 		result.StateBlockNIDs = make([]types.StateBlockNID, len(stateBlockNIDs))
@@ -112,6 +112,9 @@ func (s *stateSnapshotStatements) bulkSelectStateBlockNIDs(
 			result.StateBlockNIDs[k] = types.StateBlockNID(stateBlockNIDs[k])
 		}
 	}
+	if err = rows.Err(); err != nil {
+		return nil, err
+	}
 	if i != len(stateNIDs) {
 		return nil, fmt.Errorf("storage: state NIDs missing from the database (%d != %d)", i, len(stateNIDs))
 	}